A technical problem in connection with such rooms is that the building structure defining the room must be sealed in a fluid tight manner in order to avoid water from penetrating into the wall and floor construction, which if occurring often results in rot in the structure which in turn requires a very expensive reconstruction of the structure.
While many—and excellent—solutions today exist for fluid tightening the walls and floor of such rooms no real solution to the problem regarding fluid tightening around the drain has been provided until now.
Fluid tightening around the drain is considered by experts to be a very delicate problem. Developments of today's drains has focused on adaptation of a sealing technique in which an initial liquid sealing compound (a membrane) is applied beneath the floor tiling, for tightening the floor at the intersection between the drain and the floor.
When using a conventional drain, i.e. a square shaped or circular drain, the drain must be placed at a distance from the walls of the structure to provide a sloping surface for leading water towards the discharge outlet. In this connection, the following problems/drawbacks are often experienced:                the drain cannot properly be fixed,        the grating of the drain is not level with the floor covering        the drain is often misaligned during construction of the structure,        the drain often tilts during construction of the structure,        the drain cannot be placed very close to the structure's walls,        the drain must be placed in the walking area of the structure,        the construction's floor must be adapted to receive the drain,        additional reinforcement must be included in the area around the drain,        any reinforcement must be cut out around the drain,        the floor is vulnerable in an area around the drain,        the floor must be provided with a four-sided slope towards the drain; however, problems with water flowing in wrong directions with generation of pools of water are often encountered in the final structure,        the joint between wall and floor close to the drain is very vulnerable with respect to leaks, as the drain does not guarantee a seal between wall and floor,        the joint between the floor and drain is vulnerable with respect to leaks,        the drain does not guarantee a sealed joint between walls and floor,        the floor tiles must be cut around the drain, i.e. no possibility to hole tiles around the drain is normally present,        floor tiles cannot be laid down so as to produce the four sides inclination, which results in plain and non-functional floor tiling,        cleaning of the drain is difficult,        it is difficult to guide the water towards a small drain,        the construction of the structure is difficult and results often in serious construction errors, which at the same time increased the construction time.        
It is an aim of the present invention to provide a drain and a building structure eliminating some or all of these problems/drawbacks.